. A catalogue and price-list of drawing instruments . accurate we construct it, it is very accurately fitted with a washerbetween two flat, circular-bearing surfaces, which areclamped together by means of the conical points of twoopposite screws carried in a head of German silver, themetal of which has been hammered to make it stiff andof reliable elasticity. This arrangement is based uponcorrect theory. It ensures a uniform pressure and amountof friction in all positions of the legs of the instrument, so that when thejoint is once adjusted to suit the requirements or fancy of th
. A catalogue and price-list of drawing instruments . accurate we construct it, it is very accurately fitted with a washerbetween two flat, circular-bearing surfaces, which areclamped together by means of the conical points of twoopposite screws carried in a head of German silver, themetal of which has been hammered to make it stiff andof reliable elasticity. This arrangement is based uponcorrect theory. It ensures a uniform pressure and amountof friction in all positions of the legs of the instrument, so that when thejoint is once adjusted to suit the requirements or fancy of the user, it willhave the same stiffness or feel in all positions, and will retain it. In the cheap imitations of this joint, the friction does not depend uponthe spring pressure of the head. In consequence of this, the joint soonbecomes loose, and any attempt to tighten it will prove unsuccessful, becausethe clamping-head is made of a simple casting which possesses no elasticityand will permanently and continually bend under the strain of the Knuckle-joints. Each leg is provided with a knuckle-joint to enable theneedle-point and the pencil or pen to be kept approximately per-pendicular to the paper in making circles o\~ any radius within thecapacity of the instrument. These joints arc carefully fitted andpossess the same stiffness in all positions. They arc secured D)screws, so that this stillness can be adjusted to suit the fancy ofthe user. In (heap instruments, these are rivets with imitation screw-heads, it being impossible to cut a thread in the instrumentthat will hold, on account of the metal being a sott casting : SOKnuckle-Jolnts, that when the joint becomes loose, as it invariabh does on accountOf the bad fitting, there is no of tightening it, ami the tool is UMlcsvcataloguepriceli00alte
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectdrawing, bookyear1892
